Premium gas, more details

On some car club owner web sites, some users insist that not using Premium fuel in newer vehicles where the manufacturer recommends it, will not only rob performance but will hurt the vehicle in the long run causing the need for expensive repairs. Others say that using regular may reduce performance but that the car’s computer can adjust for it, so that no permanent damage would be done. My question is with regard the 2006 Subaru Imprez WRX with the turbo charger.

Personally, I would not “cheap out” on the octane of gas with a turbocharged engine.
However, you should abide by what the engineers who designed the engine have to say on the topic.
Simply open the Owner’s Manual, and read the specific advice on the topic of gas octane for a WRX.

If the manual states, “premium gas recommended”, that means you can use lower octane gas–albeit with a reduction in engine power and a reduction in gas mileage. Ergo–no probable saving on fuel costs in the long run.

If the manual states, “premium gas required”, I think that is quite unambiguous.
In that case, use lower octane gas only if you don’t mind risking engine damage–in addition to getting less power and lower gas mileage.

And, then there is the inevitable question:
Why buy a high-performance car if you don’t want to do what is necessary to retain the high performance that you paid for?

I would use premium for any turbo car where it is either ‘recommended’ or ‘required’. Turbos put greater load on the engine, and one of their major issues is pre-ignition, which premium addresses. Even if the engine computer is smart enough to avoid damage by reducing advance and/or boost, you’re losing some of the performance you paid extra for with a turbo.

What everyone else said. First, yes, it will damage the engine over time. And even if it didn’t, and only hurt performance, if you don’t care about performance why did you spend all that money for a WRX? You could have gotten a Civic Hybrid and saved even more money at the pump.

Not necessarily damage, anything recent will be able to retard timing enough to prevent damage, but you right on the rest.

A better answer is “sometimes” a computer can account for the less than required fuel. Car makers do not spend time programming for lazy cheap skate owners who cannot afford the proper fuel. They spent the time using the proper fuel in testing.

A recent case an auto writer was driving a Cadillac SRX with turbo V6 with a regular fuel where the motor required premium. It caused pre-ignition causing severe engine damage destroying the engine. They have since recalled it for a programming update.

So will regular work in a premium car. Maybe or maybe not. Are the effects long term or short term. Again who knows, no one has an definitive proof either way.

I do know with my 04 WRX you get a large drop in power and less MPG which yields no costs savings.

The Caddilac SRX could not retard the timing:

Nor can the Acura TL. It can retard it enough to mitigate damage if you have to fill up with regular because premium isn’t available for one or two tanks, but it can’t completely prevent predetonation on regular.

It depends on the car. It the owner’s manual says it “recommends” higher octane, you can safely use regular, although you may not save much. If it says it requires high octane, then you use it or risk serious (expensive) repairs.

If you bought this used, or are thinking about it, and the previous owner has been using low octane fuel, pass it by.